1. Technical Field
The present invention relates to a biocompatible sorbent having a vateritic nanoporous structure, a method in which the sorbent is obtained, and a method in which the sorbent is incorporated into a solid phase extraction measurement method for determining polycyclic aromatic hydrocarbon content.
2. Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
In recent times, the search for new advanced materials has been the focus of numerous research interests. Due to their potential applicability, researchers are now dedicating much effort to the study of these materials, with continuous inspiration derived from nature through Biomimicry—a recent research area that seeks to understand and take inspiration from natural phenomena in order to solve human problems (R. Lakshminarayanan, et al., “Structure-function relationship of avian eggshell matrix proteins: a comparative study of two major eggshell matrix proteins, ansocalcin and OC-17”, Biomacromolecules, vol. 6, no. 2, pp. 741-751, 2005—incorporated herein by reference in its entirety). Of particular interest are the biomineralization processes by which living organisms produce minerals often to harden existing tissues. An example is the eggshell which is predominantly composed of calcium carbonate (CaCO3) (S. Suzuki, “Black tea adsorption on calcium carbonate: A new application to chalk powder for brown powder materials”, Colloid Surface A, vol. 202, no. 1, pp. 81-91, 2002—incorporated by reference herein in its entirety). In the field of analytical chemistry, great attention has been paid to nanoporous materials from different sources including CaCO3 from waste avian eggshells. The electrostatic nature of CaCO3 particle and its porous architecture make it a promising candidate as a solid sorbent for the extraction of polycyclic aromatic hydrocarbons (PAHs).
PAHs are ubiquitous pollutants that are found in different environmental matrices at different concentrations (G. D. Nessim et al., “Precursor gas chemistry determines the crystallinity of carbon nanotubes synthesized at low temperature”, Carbon, vol. 49, no. 3, pp. 804-810, 2011; H. Yin et al., “Polycyclic aromatic hydrocarbons (PAHs) pollution recorded in annual rings of gingko (Gingko biloba L.): Regression analysis and comparison to other pollutants” Microchemical Journal, vol. 98, no. 2, pp. 303-306, 2011—each incorporated herein by reference in its entirety). Significant accumulation of PAHs in the aquatic ecosystem had been caused by anthropogenic inputs like oil spills, sea navigation, urban runoff, water and industrial wastes (B. Wu et al., “Risk assessment of polycyclic aromatic hydrocarbons in aquatic ecosystems”, Ecotoxicology, vol. 20, no. 5, pp. 1124-1130, 2011; Y-W. Hong et al., “Accumulation and biodegradation of phenanthrene and fluoranthene by the algae enriched from a mangrove aquatic ecosystem”, Marine Pollution Bulletin, vol. 56, no. 8, pp. 1400-1405, 2008; P. A. H. Westley et al., “Natural habitat change, commercial fishing, climate, and dispersal interact to restructure an Alaskan fish metacommunity” Oecologia, vol. 163, no. 2, pp. 471-484, 2010—each incorporated by reference herein in its entirety). High concentrations of PAHs are found in marine coastal environment near cities and industrial plants (K. Opuene et al., “Identification of perylene in sediments: Occurrence and diagenetic evolution”, International Journal of Environmental Science and Technology, vol. 4, no. 4, pp. 457-462, 2007—incorporated by reference herein in its entirety). Initially, concern about PAHs was only focused on their carcinogenic property (P. Boffetta et al., “Cancer risk from occupational and environmental exposure to polycyclic aromatic hydrocarbons”, Cancer Causes and Control, vol. 8, no. 3, pp. 444-472, 1997; H. Rubin, “Synergistic mechanisms in carcinogenesis by polycyclic aromatic hydrocarbons and by tobacco smoke: a bio-historical perspective with updates”, Carcinogenesis, vol. 22, no. 2, pp. 1903-1930, 2001—each incorporated herein by reference in its entirety). Recently, however, searchlight has been beamed on their antagonism of hormonal functions and their potential effect on reproduction in humans, as well as their ability to depress immune function (H. Uppstad et al., “Sex differences in susceptibility to PAHs is an intrinsic property of human lung adenocarcinoma cells”, Lung Cancer, vol. 71, no. 3, pp. 264-270, 2011—incorporated by reference herein in its entirety). These concerns have prompted both the World Health Organization (WHO) (WHO. Guidelines for Drinking Water Quality, First Addenndum to Third Edition, Geneva, 2006—incorporated by reference herein in its entirety) and the United States Environmental Protection Agency (USEPA) (U.S. EPA. National Primary Drinking Water Standards, 2003—http://www.epa.gov/safewater March 2011—incorporated herein by reference in its entirety) to formulate regulations for the protection of drinking and source water systems in order to safeguard the populace from such harmful pollutants, many of which are considered as potential carcinogens. For many superficial water systems, the European Union (EU) has set maximum admissible concentrations of 100 ng/L for both anthracene and fluoranthene, and 1200 ng/L for naphthalene (E.U. Directive 2008/105/EC, 2008, Official Journal of the European Communities L-348/84 (24th December, 2008), Council Directive (16th December, 2008) on environmental quality standards for water policy—incorporated herein by reference in its entirety).
Development of methodologies for the analysis of PAHs is, therefore, one of the important aspects of environmental analytical chemistry (N. Li et al., “Solid-phase extraction of polycyclic aromatic hydrocarbons in surface water. Negative effect of humic acid”, Journal of Chromatography A, vol. 921, no. 2, pp. 255-263, 2001—incorporated herein by reference in its entirety). In this regard, on-line and off-line solid-phase extraction (SPE) has been widely studied for trace analysis of PAHs (Y-Y. Zhou et al., “Exploration of coordination polymer as sorbent for flow injection solid-phase extraction on-line coupled with high-performance liquid chromatography for determination of polycyclic aromatic hydrocarbons in environmental materials” Journal of Chromatography A, vol. 1116, no. 1-2, pp. 172-178, 2006—incorporated herein by reference in its entirety). It can be combined with gas chromatography-mass spectrometry (GC-MS) or gas chromatography-flame ionization detector (GC-FID). Unfortunately, due to their mainly non-polar nature and adsorption onto walls of extraction vessels, PAHs are not very amenable for multistep extraction procedures such as SPE and liquid-liquid extraction (G. A. Junk et al., “Organics in water: solid phase extraction on a small scale”, Analytical Chemistry, vol. 60, no. 5, pp. 451-454, 1998; M. Rezaee et al., “Determination of organic compounds in water using dispersive liquid-liquid microextraction”, Journal of Chromatography A, vol. 1116, no. 1-2, pp. 1-9; S. Lundstedt et al., “Pressurised liquid extraction of polycyclic aromatic hydrocarbons from contaminated soils”, Journal of Chromatography A, vol. 883, no. 1-2, pp. 151-162, 2000; T. Guilherme et al., “Comparison Between Different Extraction (LLE and SPE) and Determination (HPLC and Capillary-LC) Techniques in the Analysis of Selected PAHs in Water Samples”, Journal of Liquid Chromatography and Related Technologies, vol. 28, no. 19, pp. 3045-3056, 2005; P. K. Wong et al., “The accumulation of polycyclic aromatic hydrocarbons in lubricating oil over time—a comparison of supercritical fluid and liquid-liquid extraction methods”, Environmental Pollution, vol. 112, no. 3, pp. 407-415, 2001—each incorporated herein by reference in its entirety). These techniques may also involve large solvent volumes which may not be in consonance with good environment-conscious practices. A greener approach should involve fewer steps and minimization of solvent waste. Solvent minimization through the use of commercial polymeric materials for sorption in solid-phase microextraction (SPME) (H. Bagheri et al., “An aniline-based fiber coating for solid phase micro extraction of polycyclic aromatic hydrocarbons from water followed by gas chromatography-mass spectrometry”, Journal of Chromatography A, vol. 1152, no. 1-2, pp. 168-174, 2007; R. B. Gomes et al., “Determination of total and available fractions of PAHs by SPME in oily wastewaters: overcoming interference from NAPL and NOM”, Environmental Science and Pollution Research International, vol. 16, no. 6, pp. 671-678, 2009; X. Yan et al., “Array capillary in-tube solid-phase microextraction: A rapid preparation technique for water samples”, Journal of Chromatography A, vol. 1244, no. 29, pp. 69-76, 2012—each incorporated herein by reference in its entirety) and stir bar sorptive extraction (SBSE) (B. Kolahgar et al., “Application of stir bar sorptive extraction to the determination of polycyclic aromatic hydrocarbons in aqueous samples”, Journal of Chromatography A, vol. 963, no. 1-2, pp. 225-230, 2002; J-F. Liu et al., “Use of ionic liquids for liquid-phase microextraction of polycyclic aromatic hydrocarbons”, Analytical Chemistry, vol. 75, no. 21, pp. 5870-5876, 2003—each incorporated herein by reference in its entirety) have been attempted for the analysis of PAHs in water. However, these materials are often expensive. Alternative sorption material that can carry out this function at a lower cost and offers more convenience in handling is preferred.
Solid-phase microextraction (SPME) techniques is a favored method for sampling of analytes. References describing SPME techniques, specifically as regards to explosives detection include “Trace Analysis of Explosives in Seawater Using Solid-Phase Microextraction and Gas Chromatography/Ion Trap Mass Spectrometry”, S. A. Barshick and W. H. Griest, Anal. Chem. 1998, 70, 3015-3020; “Trace Explosives Signatures from World War II Unexploded Undersea Ordnance”, M. R. Darrach, A. Chujian, and G. A. Plett, Environ. Sci, Technol. 1998, 32, 1354-1358; “Application of Solid-Phase Microextraction to the Recovery of Organic Explosives”, K. P. Kirkbride, G. Klass and P. E. Pigou, J. Forensic Sci., 1998, 43(1), 76-81. Each of the references cited above describes generally the use of SPME fibers. Typically, such fibers are fine (about 0.25 mm OD) silica fibers coated with a thin layer of a sorbing material. SPME fibers are often coated with a sorbent chosen or engineered to have a high propensity to sorb certain analytes of interest. The fibers are exposed to a gaseous or liquid environment from which a target analyte sample is to be extracted.
After a sample is collected, the fiber can then be conveniently inserted into a gas chromatograph (GC) by placing the fiber into the inlet of a GC apparatus. One common way to accomplish this is to use a needle to puncture a septum covering the GC inlet, and a syringe plunger to push the fiber (containing sorbed analytes) through the needle into the GC apparatus. Next, the fiber is rapidly heated to drive off the analytes sorbed to the sorbent substance coating the fiber. The analytes are then swept into the GC column for normal separation and quantitation.
Typically, SPME sampling involves placing the SPME fiber in the headspace above a contaminated or potentially contaminated test subject material (e.g., soil). Analytes then passively diffuse through the headspace and some ultimately adhere to the fiber. For gaseous samples of low concentration (such as in the case with explosives in soil gases), diffusion of the analytes through the gas to the SPME fiber can be a rate limiting step, resulting in long sampling times. This is especially true for instances wherein it is necessary for equilibrium to be reached, as is the case, frequently, in quantitation studies. “Solid-Phase Microextraction”, Z. Zhang, M. J. Yang and J. Pawliszyn, Anal. Chem. 1994, 66(17), 844A-853A; “Headspace Solid-Phase Microextraction”, Z. Zhang and J. Pawliszyn, Anal. Chem. 1993, 65, 1843-1853.
SPME has been shown to successfully collect target analytes in low concentration in gases and liquids. An opportunity, however, exists for optimization of SPME techniques, and further, a need remains for an optimized method and apparatus for extracting target analyte substances from volumes of gases containing those substances in low concentration. The need is especially apparent as regards to overcoming problems associated with slow equilibration and long sample times.
In another SPME process, a coated or uncoated fiber housed within a needle of a syringe is brought into contact with components/analytes in a fluid carrier or headspace above the carrier for a sufficient period of time for extraction of the analytes to occur onto the fiber or coated fiber. Subsequently the fiber is removed from the carrier or headspace above the carrier and the analytes desorbed from the fiber generally by thermal desorption into an analytical instrument, such as a gas chromatograph (GC), for detection and quantification of the analytes.
SPME has been shown to be a very useful sample preparation technique for a variety of analytes. However, SPME extraction and detection has some very serious limitations. One particularly serious limitation is in relation to attempting to utilize SPME for extractions of trace organic analytes in organic solvent carrier matrices. Basically, SPME generally cannot be applied to extraction of trace amounts of organic analytes from organic solvent carrier matrices, such as hexane. Attempts to apply SPME to extraction of trace amounts of organic analytes from organic solvents carrier matrices do not provide acceptable results because the solvent matrix is extracted by the coated fiber of the SPME device. SPME fibers for extraction of organic analytes are generally coated with an organic phase, such as the non-polar poly(dimethylsiloxane) (PDMS). Instead of the trace organic analytes being adsorbed on or into the organic phase coating on the fiber, the solvent carrier matrix components are themselves adsorbed or extracted onto the organic phase due to their overwhelmingly predominant presence in the sample. This prevents selective, efficient extraction of the trace organic analytes. For this reason SPME has not found any practical applicability for extraction of trace organic analytes from organic solvent carrier matrices. Rather, SPME carrier matrices have generally comprised predominantly aqueous matrices, for example water, a water-methanol (95:5) matrix or an aqueous inorganic salt solution matrix
This is a particularly serious limitation on the use of SPME extraction procedure since many common sample enrichment and preparation techniques for organic analysis and detection of trace amounts of organic analytes in a sample involve contacting the sample with an organic solvent carrier matrix to dissolve the organic analytes in the organic solvent carrier matrix, or in some way extracting the trace organic analytes into an organic solvent carrier matrix. For example, United States Environmental Protection Agency (EPA) Methods 608 and 525.1 require liquid-liquid extraction or liquid-solid extraction of semivolatile organic compounds, such as pesticides and polyaromatic organic compounds, from aqueous samples, such as municipal and industrial discharges or drinking water, into organic solvents. Organic solvents are used because the organic solvents have a high dissolution capability/power for the organic analytes. Subsequent concentration of the extracts and analysis thereof can give reasonably good detection. However, detection sensitivity is not particularly good and generally detection of trace amounts of less than 1 ppb are difficult or impossible to obtain with a mass spectrometer. Moreover, attempts to apply SPME methodology to this type of analysis for trace organic analytes in an organic solvent carrier matrix have failed to give selective extraction of the trace organic analytes out of the organic solvent carrier matrix due to the overwhelmingly predominant presence of said organic solvent carrier matrix as mentioned hereinbefore.
Other sorbents can be used in SPME methods other than fibrous material. For example, an eggshell can be used to extract a sorbent for SPME methods. In view of the significant disposal costs for what is conventionally a waste product, and additionally, in view of current environmental practicalities which are decreasing the availability of local disposal sites (thereby further increasing disposal cost), it will be readily appreciated that finding a significant use for egg shell waste would have important financial and environmental benefits.
It is well known that the eggshell of the chicken is a biologic composite of organic matrix (membrane) and inorganic mineral (shell). The mineral of the shell is mainly calcitic calcium carbonate. The shell membranes remain non-mineralized throughout the assembly of the eggshell and the development of the embryo (Wyburn et al., 1970, Exp. Physiology 55:213). Between the shell and the membrane is a layer of foci of mineralized matrix called the calcium reserve assembly (CRA). The CRA provides the mobilized calcium for the mineralization of the skeleton of the developing embryo (Diekert et al., 1989, Poultry Science 68:1569). At the apex of each CRA is a region known as the crown The crown is a morphologically distinct structure where function is not clear. It may act to separate the resorbable calcium (CRA) and non-resorbable calcium (shell). External to the crown is the shell proper, which is approximately 250 mm in thickness and contains approximately 5 gm of calcium carbonate (Diekert et al., 1989, Poultry Science 68:1569) It is this part of the shell which acts to physically encase and protect the developing embryo (Arias et al., 1991, Matrix 11:313).
Knowledge of the various eggshell structures was critical in developing procedures for recovering and separating eggshell calcium material from the membrane. Two shell membranes surround the egg of most avian species. A thick outer membrane attached to the shell and a thin inner-membrane. Each of these membranes is composed of a network of fibers. Early studies suggested that collagen was present as indicated by hydroxylysine and the digestion of eggshell membrane by collagenase. The presence of Type I and Type V collagen were established in the membrane by Wong (Wong et al., 1984, Developmental Biology 104:28) and Arias (Arias et al., 1991, Matrix 11:313) Other studies (Leach et al., 1982 Poultry Science 61:2040) showed that a unique protein containing lysine-derived cross links was present. Recent studies have identified, among other constituents, type V and X collagen and proteoglycans (mammillan, a keratan sulfate proteoglycan, and ovoglycan, a dermatan sulfate proteoglycan), whose localization depends on a topographically defined and temporally regulated deposition. (Soledad F. et al., 2001, Matrix Biol. 19:793).
Chicken eggshells (ES), currently an environmental nuisance, are excellent reactive agglomerates that depict sustained high reactivity towards carbonation over multiple CCR cycles. The typical dry eggshell, an excellent bioceramic composite, comprises two predominantly calcitic (CaCO3) layers and the innermost shell membrane layer. The organic material in the eggshell has excellent calcium binding properties and leads to a strong calcitic shell by self-organizing the calcite crystals during the natural eggshell formation process. Poultry eggs, used for a variety of products, result in massive amounts of eggshell waste that incur expensive disposal costs. The average annual per capita egg consumption in the United States is about 257 in 2001. However, annual eggshell wastes from various hatcheries and egg breaking industries amount to over 190,000 tons. Current disposal options include the most basic landfill, land applications including soil mixing and organic farming, and recycling in poultry diets. Of these, landfill is the easiest option as other alternatives involve significant processing costs. Eggshells, considered as organic wastes, require about $20-40/ton for landfill disposal in the U.S. This problem is further exacerbated in European countries where land prices are at a premium. In addition, landfill taxes in the United Kingdom increase this disposal cost to about 30-50£/ton. Therefore, the usage of refuse eggshells in this high temperature CO2 capture technology as reactive agglomerates is simultaneously a comprehensive solution to two global environmental concerns.